Wind force resistance of windows with tilt sash is often a problem, because a tilt sash is designed to tilt inward in the same direction that wind force drives against the sash. If the wind resistance of the sash is made especially strong, the sash will be difficult to tilt; and if the sash is made easy to tilt, it may also yield too readily to wind force. Sweep locks at check rail level can greatly increase the wind force resistance of a tilt sash that is closed and locked; but even with the assistance of check rail locks, tilt sashes can blow inward when buffeted by hurricane force winds, because the jambs for tilt sash offer less wind force resistance along the stile edges of the sash.
The wind force resistance problems of tilt sash have been difficult to solve because of the conflict between the need for easy tilting convenience and strong wind resistance. The problem also becomes more severe as tilt windows are required to provide increasingly strong wind resistance so that they can be certified not to fail in high winds. The many attempts that have been made to solve the wind resistance problems of tilt sash have not yet proved satisfactory at meeting the needs of high wind resistance at a low cost without interferring with the ease and convenience of operating the window.